Studies on the preparation and exchange reactions of 5-deuterated uracils

The mechanism of base catalyzed proton exchange at the 5-position of uracil and its N-methylated derivatives has been studied. These reactions proceed by addition — elimination across the 5,6-double bond when the 1-nitrogen is substituted with a methyl group, or with anchimeric assistance of the N-1 anion if the 1-position is unsubstituted. The base catalyzed hydrolyses of 1,3-dimethyluracil and 3-methyluracil also appear to proceed through hydrated intermediates. A facile method for an acid catalyzed preparation of 5-deuterated uracils is described as well as a simple and accurate method for analysis of deuterium content.     

Mass spectrometric determination of the heats of formation of the silane bromides

The reaction of SiBr₄(g) with H₂(g) in the temperature range 900–1143 K has been studied by a mass spectrometric method. Second and third law reaction enthalpies were obtained for SiBr₄(g) + H₂(g) = SiHBr₃(g) + HBr(g), SiHBr₃(g) + H₂(g) = SiH₂Br₂(g) + HBr(g), and SiH₂Br₂(g) + H₂(g) = SiH₃Br(g) + HBr(g). From the heats of reaction, third-law ΔH_£298 values of ?72.5 ± 1, ?43.2 ± 1.5 and ?15.3 ± 0.5 kcal/mole were obtained for SiHBr₃(g), SiH₂Br₂(g), and SiH₃Br(g), respectively.     

Urea oxidation electrocatalysis on nickel hydroxide: the role of disorder

Journal of Solid State Electrochemistry - The urea oxidation reaction (UOR) is an important challenge in electrocatalysis, in the context of electrolyzers, fuel cells, medical sensing, and...     

An Improved Synthesis of Ethylidenecyclobutane

In our studies of the chemistry of small rings, it was necessary to synthesize ethylidenecyclobutane 1. Repetition of the only method in the literature^2,3 was attempted, namely, the reaction of 1,1,1-tris-(hydroxymethyl)-propane 2 with phosphorus tribromide to give 1,1,1-tris-(bromomethyl)-propane 3 and the subsequent conversion of 3 to 1 with zinc. The reaction of 2 with phosphorus tribromide is exceedingly hazardous. In spite of the careful adherence to the conditions specified by Derfer, et. al.² there were several fires in the effluent gases and the reaction produced precipitates which ignited spontaneously in air.     

The asphericity of random 2‐dimensional complexes

We study random 2‐dimensional complexes in the Linial–Meshulam model and prove that for the probability parameter satisfying a random 2‐complex Y contains several pairwise disjoint tetrahedra such that the 2‐complex Z obtained by removing any face from each of these tetrahedra is aspherical. Moreover, we prove that the obtained complex Z satisfies the Whitehead conjecture, i.e. any subcomplex is aspherical. This implies that Y is homotopy equivalent to a wedge where Z is a 2‐dimensional aspherical simplicial complex. We also show that under the assumptions where c > 3 and , the complex Z is genuinely 2‐dimensional and in particular, it has sizable 2‐dimensional homology; it follows that in the indicated range of the probability parameter p the cohomological dimension of the fundamental group of a random 2‐complex equals 2. © 2013 Wiley Periodicals, Inc. Random Struct. Alg., 46, 261–273, 2015